Tying this ecosystem together is iCloud, and it’s the growing presence of iCloud in Apple products that marks the transition from the personal computer for the consumer. In short, Apple—like Amazon, Google, Microsoft, and others—is driving hard to teach consumers about the personal cloud experience and get them to set their expectations that content will flow seamlessly from device to device and location to location.

iCloud is Apple’s collection of personal cloud services and applications where users store, sync and share content on a contextual basis. This allows their content to be available as needed, flowing from device to device, screen to screen, and location to location no matter whether that device is a Mac, iPad, iPhone, Apple TV or some future mythical device not even on the market that can tie into the cloud functionality.

iCloud and personal cloud services are often viewed as synonymous with online storage. That is, some PC in the sky replaces my local hard drive. While storage is a key part of personal cloud services, so too are synchronization, sharing, and streaming. It is in all of these aspects that iCloud empowers the consumer.

The idea of tying consumer loyalty to personal cloud services changes the landscape where consumer platform adoption was largely driven by application availability on a single platform. That was one reason why Microsoft did so well in the PC era. The fact that personal cloud services can be driven across consumer-connected screens changes consumer perception of the importance of a given platform or device to the importance of a total ecosystem.

Apple’s ownership of both the device and software integration make what it offers among the most complete end-to-end ecosystems for personal cloud services: It allows the company to deliver a consistent experience across all Apple devices. Where needed, Apple now benefits from the large installed base of iOS devices. No wonder that the company is deepening iCloud support into the next version of OS X—Mountain Lion—to be released later in 2012.

No matter if you call it the post-PC world or the PC Plus world, the era of the personal computer has evolved. For the consumer, the personal cloud and the entire ecosystem of devices and services will help drive new customers and retain old ones. Companies that have invested into this new paradigm will see the greatest success. And that’s why iCloud isn’t just a feature for Apple devices and platforms, it’s the key that will determine the company’s success in the future.

[Michael Gartenberg is an analyst and long-time Mac user who covers the world of the interconnected consumer for Gartner. The opinions expressed are his own.]

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